Tag development expertise creates smaller, lighter, wide-range bat tracking technology

Brown bat with its wings spread, flying.

A new PNNL project will develop and evaluate smaller, longer-lasting tags for migratory bats. Photo courtesy of Shutterstock

DOE is promoting the advancement of efficient and clean wind energy production, but it is also committed to safeguarding wildlife populations, including bats, from potential issues presented by wind turbine installations.

Bats are agricultural rock stars. They eat insects, which reduces the amount of pesticides that farmers need to safeguard their crops. And bats pollinate over 700 plants—many of which are used for food and medicine. In fact, research suggests that without bats, annual North American agricultural losses could total more than $3.7 billion.

Wind turbines impact several species of bats, especially tree roosting hoary, eastern red, and silver-haired bats. It appears as though some bat species may be attracted to wind turbines, but questions remain about this relationship, such as how far away bats are attracted by the turbines and why. While endangered species of bats are affected much less by wind power plants than some other species, more information and tools are needed to research bat behavior around turbines to help design solutions to protect them.

One such tool is the radio frequency (RF) transmitter. Although these transmitters are not new to bat tracking research, the technology has been limited by transmitters that are relatively large compared to the size of bats. Biologists have recommended that transmitters be less than 5% of the bat’s body weight. For example, the smallest currently available transmitter weighs 0.22 grams (g), but some species of the endangered Myotis bat weigh in at as little as 4 g—so transmitters to track those bats should weigh less than 0.2 g. Current RF transmitters also have a short service life of typically less than 2 weeks.

To address these size and service-life challenges, in January 2019 Pacific Northwest National Laboratory (PNNL) began a 3-year, DOE Wind Energy Technology Office-funded project to dramatically improve RF transmitters with multiple versions tailored to hoary, eastern red, and silver-haired bats, as well as the Myotis species. These state-of-the-art transmitters will be paired with a three-dimensional localization algorithm to provide high-resolution behavioral information about flight patterns, which will help answer questions about how bats respond to turbines on the landscape.

Three new tag technologies are being developed and evaluated. The first minimizes the transmitter size and achieves a weight of only 0.15 g—small enough for the little Myotis bat. The second lengthens the service life for tags that track migration habits of the hoary, eastern red, and silver-haired bats, while keeping tag weight within 5% of body weight for each of these species. The third improves detection range while also maintaining weight recommendations. The detection range improvements are expected to be useful for studying the attraction of bats to wind turbines, as well as for observing their movements across one or more wind plants.

This is not PNNL’s first foray into wildlife tagging. The lab’s research team has vast expertise in tag development, including transmitters and batteries small enough to be injected into tiny young fish, eliminating stress caused by surgical tag implementation. More than 100,000 fish in the United States, Australia, Brazil, Germany, Belgium, and East Asian countries have been tracked and studied using versions of PNNL tags.

Going forward, PNNL’s new bat tagging and tracking tools could help wind energy developers and operators realize shortened permitting time and reduced costs—while also benefiting the bat population, agriculture, and the environment.